The present invention relates to interfaces between solids and fluids or between two kinds of fluids, more particularly to methods and apparatuses for performing measurements relating to surface waves described by such interfaces.
Seakeeping characteristics of a surface ship are of the utmost concern to the designer of the marine vessel, whether it be a naval combatant, a commercial cargo ship or a pleasure cruise liner. A common paradigm in the design process involves the usage of computational fluid dynamics (CFD) techniques to compute the influence of surface waves on the motion of the ship in different sea states. The surface wave input to the ship motion calculation can be from an assumed wave spectrum, or from a solution of a CFD computation, or from a measured wave based on a physical experiment. Experimental measurement of surface waves is thus important either as a direct input to the computation of the ship motion or as a verification of the accuracy of CFD computation of the surface wave field.
Many measurement techniques, such as sonic probes and finger probes, have been employed to measure surface wave elevation at a few discrete locations. However, to date no technique exists that would allow the instantaneous measurement of the surface wave field at a large array of points around a ship model. In order to use discrete point measurements as input to the ship motion calculation, certain assumptions need to be made regarding the spatial uniformity of the wave field. The validity of these assumptions depends highly on the complexity of the wave field and can therefore put the results into question. Simultaneous field measurements of the surface waves taken at a large array of points, and covering a large physical area, would be more suitable—both for the purpose of providing a direct input to the ship motion calculation and for the purpose of validating a CFD computation of a wave field.